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When the Cassini space probe makes its final descent into Saturn later today, data from the final nine hours of the mission will be sent back to NASA’s tracking station in Canberra, Australia.

As the probe descends, it will capture images and data from Saturn and its atmosphere, revealing more of the planet’s secrets. Under the spacecraft’s normal operations, its instruments first store and later forward images and data to Earth.

But in Cassini’s final hours, it will be transmitting home in real time, with the signals picked up by the CSIRO-managed Canberra Deep Space Communication Complex (CDSCC).

How to destroy the probe

NASA decided to safely dispose of Cassini into Saturn, ending its mission as a shooting star. With the spacecraft nearly out of fuel and possible loss of control, this plan will prevent accidental collisions with any of Saturn’s moons and potential biological contamination by microbial stowaways from Earth.

Viewed from Saturn, the last moments of Cassini would look similar to a meteor entering Earth’s atmosphere.

An illustration of Cassini breaking apart after entering Saturn’s atmosphere.NASA/JPL-Caltech

From Earth, the world will await the bittersweet moment when NASA’s Jet Propulsion Laboratory mission control announces loss of signal. Cassini’s final call home will have been made.

It will mark the end of a 20-year mission, a joint venture between NASA, the European Space Agency and the Italian Space Agency.

Mission objectives

Inspired by the earlier flypast by the twin Voyager spacecraft, the two-part mission was actually known as the Cassini-Huygens mission.

The main craft was designed to study Saturn and its environs, while the piggybacking Huygens probe was to land on Titan, the planet’s largest moon.

Throughout its odyssey, every step of Cassini’s journey has been followed by the dishes at CDSCC in Canberra. It was the first tracking station to make contact with Cassini after its launch from Cape Canaveral in October 1997.

The Cassini spacecraft and Huygens probe begin their seven-year journey to Saturn after a successful launch on October 15, 1997.NASA

It then tracked Cassini throughout its seven-year journey to Saturn, handling the vital communications as it arrived and was placed into orbit around the planet in July 2004.

It was also used to map the terrain and depths of ethane and methane lakes on the surface of Titan. For Cassini’s final bistatic observations of Titan earlier this year, key members of Cassini’s science team travelled to Canberra to witness the data coming into CDSCC first-hand.

Staff found it exhilarating to watch the pure excitement on the faces of Cassini’s team standing in their Canberra control room as the spacecraft’s faint signals were being received.

Bistatic scattering reveals the details on Titan.

To some of us, the data may have appeared as not much more than a slightly higher peak in a hash of radio noise, but to the mission team it meant discovering a shoreline or a lake bottom on the surface of a world more than a billion kilometres away. Being a part of these discoveries was a proud moment for CDSCC and its CSIRO team.

The rest of the probes

As we say goodbye to Cassini, CDSCC continues to track more than 30 other spacecraft, not only NASA probes but also those of other international space agencies in Europe, Japan and India.

Canberra Deep Space Communication Complex will keep track of other spacecraft after Cassini’s final plunge into Saturn.CSIRO CDSCC

NASA’s Juno has only just begun its primary mission, transmitting scientific data as it orbits Jupiter. Its highly elliptical orbit brings the spacecraft dangerously close to Jupiter (5,000km) before retreating away from the radiation-intense planet.

New Horizons, which flew past Pluto in 2015, has set a course for an encounter with a Kuiper Belt object on January 1, 2019. The spacecraft is periodically woken from hibernation to check system functions before being returned to slumber.

The next few years will see a quantum shift as the Deep Space Network moves to supporting proposed human missions to the Moon, asteroids and Mars.

Some key numbers for Cassini’s Grand Finale and final plunge into Saturn.NASA/JPL-Caltech

For now though, CDSCC is concentrating on Cassini’s final moments, delivering its last breath of data to NASA scientists who will continue to study the information for decades to come.

Using the big 70-metre antenna dish at CDSCC as the prime receiver, it will be backed up by a smaller 34m dish. To add even further redundancy into the system, the European Space Agency has a 35m dish in New Norcia, Western Australia, which will also listen to Cassini’s radio whispers.

Cassini’s final hours will be a bittersweet moment for the CDSCC team, losing a spacecraft that for 20 years had become a daily part of our lives.

We will say a fond farewell to an incredible mission, safe in the knowledge that we’ve been a part of an adventure that revealed Saturn as a real place, full of wonders, for future generations to explore.

I have had a most interesting couple of days on the road and in the bush. Currently I’m in a motel room at Woolgoolga, near Coffs Harbour on the mid-north coast of New South Wales, Australia. ‘Hardly the wild,’ I hear you say, and you’re quite right – it isn’t. The weather was beginning to change I noticed on the final leg of my day’s itinerary, so I decided to hide out in a motel room for the night – good decision, it’s pouring outside.

I won’t give all away – I’ll leave the main description of the holiday to the website – but just some of the ‘downlights’ of the first couple of days for this post.

I didn’t arrive at Cathedral Rock National Park until just on dark, but did get the tent up prior to darkness arriving – when it did, it was dark! The campfire took an eternity to get going as all of the timber was damp and by the time I got it started it was time for bed – all-be-it an early night (7.30pm). I had decided to not spend the money on replacing all of the gear I needed to replace for camping, following the loss of a lot of gear over the years due to storage, etc. I hadn’t done much in the way of bushwalking or camping for years due to injuries sustained in my car crash and a bad ankle injury, so I left it all a bit late. I figured that for this holiday I’d make do and replace the gear with quality gear before the next trip. In short, I’ll get by – but it would have been nice to have some good gear just the same. It was a very cold night let me tell you – and long.

When I reached the heights of my first walk today, standing on top of Cathedral Rock National Park, my digital camera decided to die on me. I knew there was something wrong with it during the ascent as it was really chugging away taking pictures. I did get a couple of reasonable panoramic shots on the top of Cathedral Rock before it died, so that was good. I took stills with the video camera I was using, so it wasn’t a complete loss. When I completed the Woolpack Rocks walk I made the trip to Coffs Harbour to seek a replacement and got one for a reasonable price. It’s just another compact and so I will also buy a digital SLR prior to my next trip I hope. My previous SLR was basically destroyed when the camera cap came off during a multiple day bushwalk and all manner of stuff got into it. It wasn’t digital so I didn’t bother repairing it.

So tomorrow – off to Dorrigo National Park I hope and several lengthy walks I haven’t done before. Hopefully the rain will clear.